The present invention relates to a method and device for controlling a pressure supplying arrangement of a brake system for delivering a pressure medium.
Conventional method and device for controlling an electro-hydraulic brake system pump are described in German Patent Application No. 195 48 248, which provides that the hydraulic fluid is introduced from an accumulator into the wheel brake cylinders via valves, the accumulator being charged by a pump. To achieve the quietest possible charging of the accumulator the pump is triggered using a pulse-pause relationship of a PWM signal suited to demand dependent on volume demand for hydraulic fluid and upon pressure in the accumulator. The PWM signal is changed depending on a specified pressure value and the deviation of the actual pressure from this value. A plurality of fixed pressure threshold values is used for proper triggering for proper delivery output. This German Patent Application specifically describes the triggering of a pump in an electro-hydraulic brake system.
In addition, conventional methods and devices describe that the return pumps of a hydraulic unit for an antilocking brake system (ABS), an automatic traction control system (ASR) or an electronic stability program (FDR, ESP) are triggered depending on the drivers braking intent. German Patent Application No. 195 01 760 describes such triggering action. In particular, this German Patent Application describes that the pressure in the master brake cylinder representing the activation of the brake pedal and thus the driver""s intent is determined by a sensor. The return pump is triggered via a threshold value comparison so that a pressure reduction, pressure increase, or pressure maintenance condition results as needed.
In addition, there are a number of documents in which various configurations of brake systems with embedded pressure supply means, in particular pumps, are described.
The conventional methods and the corresponding conventional devices are not capable of delivering optimal results in every respect. Thus, while the desired target pressure is rapidly achieved by the conventional pump triggering methods and devices, the formation of a defined pedal movement and thus of a defined pedal feel resulting from a regulated pump intake pressure is neglected because the pressure is drawn from the master brake cylinder in an unmetered manner to build up the desired pressure. In addition, this leads, in suction operation of the pump, to a shift of the characteristic of the brake system. In addition, as a result of the high pump capacity and the cavitation effects which accompany the high pump at a partial output of the pump, noticeable noise develops.
The drawbacks of the conventional methods and devices are compensated for and additional advantages are achieved using a simultaneous use or an alternative use of different pressure differentials according to the present invention for the formation of the triggering signal or for control of the pressure supplying arrangement, in particular, of a pump or a pump motor.
According to the present invention, a rapid attainment of the target pressure and a defined pedal movement (and thus a defined pedal feel) are achieved. This takes place via a controlled use of the pressure applied at the input of the pressure supplying arrangement for regulation and/or pilot control. Through the selection of a characteristic which does not have a linear gain throughout between an actual pressure and a target pressure, but rather a partially non-linear gain, the pedal movement and the pedal feel can be precisely matched to the application conditions or the intent of the driver. In addition, as a result of the use of at least one second pressure differential for regulation and/or pilot control of the pressure supplying arrangement, in particular the pump, no noise is generated by cavitation effects since the pressure supplying arrangement is always adequately preloaded through the pedal pressure exerted by the driver. In addition, suction operation of the pressure supplying arrangement is avoided through the features described above, resulting that no shift of the characteristic takes place. In addition, as a result of precise regulation and/or pilot control in the pressure supplying arrangement, the pump motor operates at a lower speed, resulting overall in a lower electrical system load and a lower noise level.